1. Field of the Invention
This invention relates to a chip removing device for removing, in a multi-head machine tool such as a wood working machine of the type wherein a plurality of working heads are selectively used, chips of wood or the like from around the working heads by way of vacuum suction while working of the workpiece is proceeding.
2. Description of the Prior Art
A chip removing device of the type mentioned has been already proposed by the inventor of the present patent application. The chip removing device is disclosed in Japanese Utility Model Publication No. 13605/1985 and has such a structure as shown in FIGS. 11 and 12. Referring to FIGS. 11 and 12, a multi-head machine tool in which the chip removing device is incorporated includes a column 1 and a ram 2 mounted for vertical up and down movement on the column 1 and connected to be moved up and down by a motor 3. A plurality of, for example, four, head holders 4 are mounted in a leftward and rightward juxtaposed relationship on the ram 2. A working head 5 is mounted for up and down movement on each of the head holders 4 and connected to be shifted between an upper position and a lower position by an air cylinder 6. Each of the working heads 5 is constructed such that a motor 9 is supported at the center within a hood 8 in which a plurality of suction air passages 7 are defined, and a connecting pipe 10 is secured vertically at the top end of the hood 8 while a brush 11 is provided vertically downwardly on a peripheral edge at the bottom end of the hood 8. A tool 12 such as a router can be removably mounted on a rotary shaft of each of the motors 9.
A duct 13 extends in a horizontal direction on the ram 2. Upper end portions of the connecting pipes 10 of the four working heads 5 are fitted for individual up and down sliding movement in an airtight condition in four holes 14 formed in a lower wall of the duct 13 and extend into the duct 13. Four valve devices 15 corresponding to the four working heads 5 are provided in a juxtaposed relationship in the duct 13. Each of the valve devices 15 includes a valve plate 17 mounted for up and down sliding movement on four guide rods 16 which are securely mounted on and extends vertically upwardly from the lower wall of the duct 13. Each of the valve plates 17 is normally urged downwardly by a compression coil spring 18. Since a stopper 19 is provided at an intermediate location of each of the guide rods 16, each of the valve plates 17 can be moved down only to a predetermined vertical position at which it contacts with the corresponding stoppers 19. A seal member 21 is provided on a lower face of each of the valve plates 17 for closing an upper end opening 20 of the corresponding connecting pipe 10 in an airtight condition.
The duct 13 is connected to a vacuum duct collector not shown. Only an arbitrary one of the four working heads 5 which is to be actually used is shifted to the lower position by the corresponding air cylinder 6 while the other working heads 5 are kept at their upper positions. The connecting pipes 10 of those of the working heads 5 which are kept at the upper positions keep, against the springs 18, the valve plates 17 at corresponding higher positions at which the upper end openings 20 thereof are pressed against and closed in an airtight condition by the seal members 21 to disconnect the suction air passages of the hoods 8 from the duct 13. Consequently, a sucking operation by way of the suction air passages 7 does not take place in the working heads 5 which are kept at the upper positions. On the other hand, the suction air passage 7 of a working head 5 which is positioned at the lower position is connected to the duct 13 by way of the corresponding connecting pipe 10 since the upper end opening 20 of the connecting pipe 10 is positioned below the vertical position of the stopper 19 and thus spaced away from the corresponding seal member 21. Accordingly, chips of wood or the like cut off by the tool 12 mounted on the working head 5 are sucked into the suction air passage 7 and introduced into the duct 13 by way of the connecting pipe 10 whereafter they are transported to a collecting station by way of the duct 13.
However, the conventional device has the following drawbacks.
The valve devices 15 which are complicated in construction must be provided individually for the working heads 5, which requires a correspondingly high cost.
Further, since the valve devices 15 are provided in the duct 13, maintenance thereof is very cumbersome.
Besides, since the valve devices 15 are secured at predetermined positions in the duct 13 such that they may correspond individually to the working heads 5, while the head holder 4 is constructed for leftward and rightward movement relative to the ram 2, the distance between adjacent ones of the working heads 5 can be adjusted but only by a very limited amount.